Kopitar got his 758th NHL assist on the go-ahead goal, scored by Quinton Byfield at 13:26 of the third period. He passed Marcel Dionne, who had 757 assists in 921 games. Kopitar did it in 1,313 games.
Byfield scored twice and Trevor Moore had a goal for the Kings (14-4-3). Cam Talbot made 20 saves.
Josh Manson got his first goal of the season, but the Avalanche (15-7-2) lost both games of a back-to-back set following a 4-3 shootout defeat at the Anaheim Ducks on Saturday. Alexandar Georgiev allowed three goals on 37 shots.
Colorado defenseman Cale Makar did not play because of a lower-body injury.
Byfield put Los Angeles ahead 2-1 at 13:26 of the third period, sitting at the top of the crease to score off Adrian Kempe’s pass. Kopitar had the secondary assist to break the tie with Dionne.
Moore made it 3-1 at 14:22, scoring on a sharp-angle shot.
Drew Doughty scored into an empty net at 18:53 for the 4-1 final.
Manson put Colorado ahead 1-0 at 12:28 of the first period. He scored his first goal on a wrist shot from the right circle.
Byfield tied it 1-1 at 9:03 of the second period, getting to the front of the crease to tip in Mikey Anderson’s shot.
